The present disclosure relates generally to a foil bearing with a split key, and more specifically, to a thin foil, hydrodynamic gear bearing comprising a split key to reduce or eliminate a non-synchronous or reverse on the thin foil, hydrodynamic gear bearing.
In general, thin foil, hydrostatic journal bearings are used to support a rotating element in air cycle machines. Historically, journal loading was assumed to be static, (due to gravity or acceleration) or synchronous (1 time per shaft rotation); however, recent experience has shown that there are environments that impose a non-synchronous, high-cycle load on the thin foil, hydrostatic journal bearings. This has led to bearing anti-rotation key cracking (and in some cases separating) initiated at a tight radius at a bottom of a formed key of the thin foil, hydrostatic journal bearing. The cracking is in part due to a geometry of the tight radius, which is an inherently high stress riser. Further, a forming operation necessary to fold the foil into a 180° bend exceeds an ultimate elongation of the foil itself, which leads to an orange peel condition and a degradation in the material fatigue strength.